diff --git a/src/wp-includes/rest-api.php b/src/wp-includes/rest-api.php
index cb6833772a765..b97dfd014be41 100644
--- a/src/wp-includes/rest-api.php
+++ b/src/wp-includes/rest-api.php
@@ -3428,7 +3428,8 @@ function rest_convert_error_to_response( $error ) {
 	$status = array_reduce(
 		$error->get_all_error_data(),
 		static function ( $status, $error_data ) {
-			return $error_data['status'] ?? $status;
+			// Note: $error_data may not be an array (e.g. stdClass), so is_array() check is intentional.
+			return is_array( $error_data ) && isset( $error_data['status'] ) ? $error_data['status'] : $status;
 		},
 		500
 	);
diff --git a/tests/phpunit/tests/rest-api/rest-server.php b/tests/phpunit/tests/rest-api/rest-server.php
index 692c363ac7595..bd3a9346f70b2 100644
--- a/tests/phpunit/tests/rest-api/rest-server.php
+++ b/tests/phpunit/tests/rest-api/rest-server.php
@@ -592,6 +592,19 @@ public function test_error_to_response_with_additional_data() {
 		$this->assertSame( array( array( 'status' => 400 ) ), $response->get_data()['additional_data'] );
 	}
 
+	/**
+	 * @ticket 64901
+	 */
+	public function test_error_to_response_with_stdclass_data() {
+		$error = new WP_Error( 'test', 'test', (object) array( 'status' => 400 ) );
+
+		$response = rest_convert_error_to_response( $error );
+		$this->assertInstanceOf( 'WP_REST_Response', $response );
+
+		// stdClass data should not cause a fatal, status should default to 500.
+		$this->assertSame( 500, $response->get_status() );
+	}
+
 	public function test_rest_error() {
 		$data     = array(
 			'code'    => 'wp-api-test-error',